Bone scan index: A new biomarker of bone metastasis in patients with prostate cancer.

Bone scintigraphy is one of the first-line imaging modalities for the screening and follow up of bone metastasis in patients with prostate cancer. The amount (%) of bone metastasis can be calculated using a bone scan index thanks to recent advances in quantitative bone scintigraphy. Since an artificial neural network was applied for hot-spot characterization and quantitation, the bone scan index has become a simple, reproducible and practical means of quantifying bone metastasis. The bone scan index is presently considered as an imaging biomarker of bone metastasis. The present article summarizes the principles and application of bone scan index using dedicated software (EXINI bone in Europe and North America; BONENAVI in Japan), and the advantages and cautions of using the bone scan index. The bone scan index could serve as a practical marker with which to monitor disease progression and treatment effects in multicenter studies, and to manage prostate and other types of cancer in the clinical setting.